England took the lead in the 14th minute when Steph Houghton drilled the ball low into the right corner from an indirect free-kick inside the penalty area.
The opener came after Cameroon goalkeeper Annette Ngo Ndom collected a back-pass from defender Augustine Ejangue, who appeared to spit on Toni Duggan.
Forward Ellen White then scored her fourth goal of the tournament as she collected a pass from defender Lucy Bronze to fire home, with VAR confirming that she was not offside after the goal was initially disallowed.
That incensed Cameroon's players, who appeared to almost refuse to restart the contest as they argued with the referee in the middle of the pitch, furiously pointing to the screen in the stadium which showed the replay, before getting into a huddle.
The match eventually continued after Cameroon coach Alain Djeumfa managed to calm his players but more anger was to follow in the second half after Ajara Nchout scored to reduce the deficit.
The forward's goal was disallowed for offside following a VAR review, leaving her close to tears amid more protests.
England added a third through defender Alex Greenwood, who swept in a first-time effort from a well worked corner in the 58th minute to rub salt into the wounds.
England meet Norway in Le Havre in the last-eight after the Scandinavians beat Australia on penalties on Sunday (AEST).
